https://community.cloudera.com/t5/Support-Questions/Issue-quot-sandbox-hdp-hortonworks-com-8020-failed-on/m-p/268857#M206440 <P><a href="https://community.cloudera.com/t5/user/viewprofilepage/user-id/35813">@shashank_naresh</a>&nbsp;</P><P>The following error can occur if the NameNode is not running fine.</P><P><STRONG>Highlighted Error:</STRONG></P><P>&nbsp;</P><LI-CODE lang="java">Call From sandbox-hdp.hortonworks.com/172.18.0.3 to sandbox-hdp.hortonworks.com:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: &lt;a href="http://wiki.apache.org/hadoop/ConnectionRefused" target="_blank"&gt;http://wiki.apache.org/hadoop/ConnectionRefused&lt;/a&gt;</LI-CODE><P>&nbsp;</P><P><STRONG>Possible cause:</STRONG><BR /><SPAN>1). Please verify if the port 8020 is actually listening?&nbsp; If not then we will need to check the NameNode log for any errors. We might need to also check the NameNode GC log to see if it has sufficient memory and if the GC is happening properly or not?</SPAN></P><P>&nbsp;</P><LI-CODE lang="python"># netstat -tnlpa | grep 8020 # netcat -tnlpa | grep 50070</LI-CODE><P>&nbsp;</P><P>2). There might be some errors listed in NameNode logs that can be found at. So can you please check and share the log file here?</P><P>&nbsp;</P><LI-CODE lang="python"># ls -l /var/log/hadoop/hdfs/hadoop-hdfs-namenode-sandbox-hdp.hortonworks.com.log # ls -lart /var/log/hadoop/hdfs/gc.log-201908*</LI-CODE><P>&nbsp;</P><P><STRONG><SPAN>Specially in case of Sandbox Environment:</SPAN></STRONG></P><P><SPAN>As Sandbox is a single node cluster for testing/learning purpose which has a lots of services running on a single host so some times we might see that due to heavy load of other running services other services like NameNode ..etc does not function properly.&nbsp;&nbsp;</SPAN></P><P><SPAN><STRONG>So please try this:</STRONG>&nbsp; Stop the services that you are not needing currently in your Sandbox. Put those services in maintenance mode form Ambari UI and then just start the services that you are testing currently.&nbsp; This should free some memory on the sandbox host and back ground processing load by those services and that should improve the scenario.&nbsp;</SPAN></P><P>&nbsp;</P> Sat, 24 Aug 2019 21:22:23 GMT jsensharma 2019-08-24T21:22:23Z